godot-shaders-basics

name

godot-shaders-basics

description

Expert Godot shader patterns for batch-safe hitflash, alpha-scissor foliage/dissolve, screenspace postFX, depth reconstruction, triplanar, and instance uniforms — not first-shader tutorials. Trigger on draw-call batching breaks, discard vs depth-prepass, foliage shadows, post-process quads, or world-position FX. Keywords: instance uniform, ALPHA_SCISSOR, hint_screen_texture, hint_depth_texture, global uniform, sampler2DArray, canvas_item, spatial, post-processing.

NEVER Do in Shaders

• NEVER use discard unconditionally for optimization — It prevents the depth prepass from working effectively. A discarded pixel still costs vertex processing; sometimes not rendering the object is better [1].
• NEVER use if/else for dynamic states in high-performance shaders — GPUs hate branching. Use mix(), step(), and smoothstep() for mathematical, hardware-optimized selection [5, 21].
• NEVER compare floats exactly — Hardware precision varies; if (v == 0.5) is unreliable. Use abs(a - b) < epsilon or step().
• NEVER use standard Alpha Blending for massive foliage — It prevents shadows and SSR. Use Alpha Scissor or Alpha Hash (dithering) to enable depth prepass and shadow casting [7].
• NEVER hardcode POSITION to vec4(VERTEX, 1.0) for full-screen quads in 4.3+ — Godot 4.3 uses Reversed-Z depth; this will cause clipping. Use POSITION = vec4(VERTEX.xy, 1.0, 1.0) [8, 9].
• NEVER duplicate materials to change one color/value on many enemies — Use instance uniform. This allows unique values for thousands of nodes while maintaining a single draw call (batching) [10].
• NEVER use TIME without a speed multiplier — Fragment speed should be controllable via uniforms to ensure consistency across different gameplay states.
• NEVER forget hint_source_color for color uniforms — Without it, the engine treats colors as linear math, leading to incorrect gamma and washed-out visuals in the inspector.
• NEVER calculate complex math in fragment() that could be in vertex() — vertex() runs once per point; fragment() runs millions of times per frame. Interpolate values via varying instead.
• NEVER use #define macros for dynamic runtime toggles — These create new shader permutations, causing massive compilation stutters when first encountered in-game. Use uniforms instead.
• NEVER forget to normalize vectors — Using reflect(dir, normal) on unnormalized vectors causes severe rendering artifacts and incorrect lighting math.
• NEVER modify UV without bounds checking or fract() — Shifting UVs beyond 0.0-1.0 without repeat wrapping or clamping will sample edge pixels or return black, breaking texture consistency.

Scenario → Script Triggers

MANDATORY for the matching effect. Do NOT Load beginner canvas_item tint recipes or built-in variable glossaries here.

Goal	Script
Per-enemy hitflash without breaking batches	MANDATORY instance_uniform_hitflash.gdshader
Foliage wind + shadows	MANDATORY foliage_wind_sway_expert.gdshader (alpha scissor/hash — not unconditional discard)
Dissolve that keeps depth-prepass	MANDATORY dissolve_scissor_expert.gdshader
PostFX pixelate / stylize	MANDATORY screenspace_hex_pixelate.gdshader
Full-screen quad (Reversed-Z)	MANDATORY screenspace_full_quad.gdshader
Depth → world for water/fog	MANDATORY depth_world_reconstruction.gdshader
Grass flatten from player	global_grass_flatten.gdshader
UV-less cliffs/rocks	triplanar_world_mapping.gdshader
Unique textures on instanced meshes	instance_texture_array.gdshader
Vertex displacement terrain	noise_terrain_displacement.gdshader
Animate uniforms at runtime	shader_parameter_animator.gd
VFX port template	vfx_port_shader.gdshader

Golden path for cutouts/dissolve: ALPHA_SCISSOR / alpha hash (see dissolve + foliage scripts) — not discard for optimization. NEVER list explains why.

Available Scripts

instance_uniform_hitflash.gdshader

Instance-uniform flashes; one material, many unique intensities.

dissolve_scissor_expert.gdshader

Mask dissolve with ALPHA_SCISSOR for depth-prepass + shadows.

foliage_wind_sway_expert.gdshader

World-space wind sway for foliage batches.

global_grass_flatten.gdshader

global uniform player interaction flattening grass.

screenspace_hex_pixelate.gdshader

hint_screen_texture stylized postFX.

screenspace_full_quad.gdshader

Reversed-Z-safe full-rect post pass.

depth_world_reconstruction.gdshader

hint_depth_texture → world position.

triplanar_world_mapping.gdshader

World-axis projection without UVs.

instance_texture_array.gdshader

sampler2DArray + instance uniform for unique batched textures.

noise_terrain_displacement.gdshader

Vertex noise displacement.

vfx_port_shader.gdshader

Validated VFX shader template.

shader_parameter_animator.gd

Tween/runtime uniform animation without AnimationPlayer.

shader_warmup_loader.gd

Pre-warm shader pipelines during loading screens to avoid first-frame stutter.

Expert Pointers

• Move invariant math to vertex(); pass via varying.
• Color uniforms need hint_source_color.
• Prefer Official Docs for shading-language builtins; this skill owns batching, scissor, screenspace, and depth routing.

Deep recipes (on demand)

LLM-ignorance rule: if a general agent would not know it before reading, it lives here or in scripts/ — never delete, only move.

Topic	Reference
2D dissolve/wave/outline	2d-effect-recipes.md
3D toon + vignette	3d-and-postfx-recipes.md
Uniforms / built-ins	uniforms-and-builtins.md
Fog, compute, warmup	expert-advanced-patterns.md

Reference

Progressive disclosure: open Official Documentation links only when researching a specific API; load Related Skills when routing work to a peer domain — do not preload the whole lattice.

Official Documentation

• Introduction to shaders — Entry map of shader types, render modes, and when to use ShaderMaterial vs StandardMaterial3D.
• Shading language — Core GLSL-like syntax: uniforms, hints, varyings, built-ins, and preprocessor rules used throughout this skill.
• CanvasItem shaders — 2D canvas_item built-ins (UV, COLOR, TEXTURE, SCREEN_UV) for sprites, UI, and 2D post FX.
• Spatial shaders — 3D spatial built-ins (ALBEDO, NORMAL, instance uniform, depth/screen textures) for materials and full-screen quads.
• Your first 2D shader — Minimal canvas_item workflow from ShaderMaterial attach through fragment tinting.
• Your first 3D shader — Minimal spatial workflow and conversion path from StandardMaterial3D into writable shaders.
• ShaderMaterial — Runtime set_shader_parameter / instance parameter API used by animators and hit-flash batching.
• Custom post-processing — Screen-reading shaders, hint_screen_texture, and compositing patterns for pixelate/vignette-style FX.
• Advanced post-processing — Depth buffer, reversed-Z, and world reconstruction needed for water/fog/debug visualizers.
• Compute shaders — RenderingDevice GPGPU path for particle sims and other non-fragment workloads.
• Using VisualShaders — Graph editor + VisualShaderNodeCustom extensibility covered in the expert patterns.
• GPU optimization — Overdraw, transparency, and batching guidance that motivates alpha scissor, instance uniforms, and vertex-vs-fragment cost.

Related Skills

Prerequisites

• godot-project-foundations — Nodes, Resources, and project layout required before attaching ShaderMaterials and shipping .gdshader assets.
• godot-resource-data-patterns — Sharing vs duplicating ShaderMaterial/Shader Resources so uniforms and instance parameters stay batch-friendly.

Complements

• godot-3d-materials — StandardMaterial3D/ORM first; graduate to spatial shaders for triplanar, dissolve, and instance-uniform effects.
• godot-3d-lighting — How custom ALBEDO/EMISSION/light() output interacts with Forward+, GI, and fog volumes.
• godot-particles — Particle process/draw materials and alpha pipelines that must match scissor/hash vs blend choices from this skill.
• godot-2d-animation — CanvasItem shader hooks for stylized 2D motion, outline, and dissolve on animated sprites.
• godot-camera-systems — Camera near/far and view/projection matrices that screen-space and depth-reconstruction shaders depend on.
• godot-performance-optimization — Draw-call batching, MultiMesh, and GPU budgets that justify instance uniform and avoiding unique materials.
• godot-debugging-profiling — GPU/overdraw profilers and debug views to validate shader cost and depth/normal visualizers.

Downstream / consumers

• godot-procedural-generation — Procedural meshes/terrain consume noise displacement, triplanar, and UV-less spatial patterns from this skill.
• godot-3d-world-building — Large environment props apply foliage wind, grass flatten, and world-projection shaders at level scale.
• godot-genre-open-world — Open-world foliage interaction, distance FX, and shared-material batching consume these shader templates.

Master

• godot-master — Library router and mirrored module entry for cross-skill discovery.